What's new in 2.4 compared to 2.3 ? Lots of cool stuff! The work was spread
on several fronts:
- performance and latency: a lot of work was done on locking reduction,
bringing 2.4 a much lower latency than 2.3 had, and a higher scalability.
2.4 is NUMA-aware on Linux and will avoid binding to cross-socket cores
by default. Idle server-side connections are now reusable even when SNI,
proxy protocol or transparent proxy are used, saving costly round trips.
Lua now supports lock-free multi-threading. Idle frontend connections
will now be closed as soon as possible during reloads.
- reliability: "strict-limits" is on by default, experimental features
are protected against accidental use from a copy-paste, a diagnostic
mode was added to report suspicious or uncommon constructs that could
be mistakes, new live debugging tools were added for better in-field
debugging. Backend idle connections will be closed before quitting
so that they don't consume source ports in TIME_WAIT.
- management and integration: maps and ACLs now support atomic updates,
server-side SSL certificates can also be updated without reloading,
servers can be added/removed without reloading (still experimental),
more server settings can be edited at run time, global variables can
be listed/edited at run time, "defaults" section can now be named,
reused an inherited, line numbers and file names can be included in
any command, file paths can now be relative to the config file, some
new ".if/.elif/.else/.endif" config directives permit a smoother
transition between versions using a same config file (particularly
useful for automated rollbacks),
- interoperability / protocol support: WebSocket over HTTP/2 (RFC8441)
is now supported on both sides, regardless of the version on the other
side. The cache now supports the "Vary" header with a few commonly
used headers, including "Accept-encoding" which gets normalized for
optimal cache hit ratio. The Prometheus exporter got a significant
liftup, requires less tricks on the Prometheus side, and supports
listing only certain metrics for faster retrieval. Optional native
support for Opentracing was also integrated (via USE_OT=1). The DNS
resolvers now support talking to servers over TCP. Basic support for
extracting information from MQTT and FIX protocol was added. Timeouts
can now be adjusted on the fly and per-request in order to adapt to
particuarly slow servers or special protocols.
- user-friendliness: TCP loggers now do not require a ring section
declaration anymore, it's transparently done now. Header deletion
using a pattern matching on the name is now supported instead of
having to list many names. Checking for real server-side errors got
easier than before with http_fail_cnt/http_fail_rate. The config
parser and CLI will now provide suggestions when some keywords are
misspelled. The CLI's help output can now be filtered to subsets of
commands and will be sorted for easier finding.
- processing: the new "wait-for-body" HTTP action allows to wait for
a request or response body up to a certain size or delay. This is
convenient to detect POST contents or to detect error patterns or
information leaks in responses. TCP frontends can now be manually
upgraded to HTTP, allowing HTTP rules to be used in a frontend in
a tcp->http scenario. JSON parameters can be decoded to extract some
fields values. A URL encoder is now available to pass some fields in
a way that is suitable for query string parameters. Base64 variants
are now supported (such as the URL-compatible one used by JWT).
- for distros: building optional addons will be easier thanks to the
removal of the contrib/ directory and the cleaner integration with
the regular build process and include files. Libslz was included by
default, simplifying the packaging work. A few example configs were
added into examples/ to serve as starters for users. A CPU entry was
added to produce executables that works well both on old and new
ARMv8 CPUs.
- observability: more stats were added (SSL, H2). "show info" can now
emit floating point values for rates and uptimes if requested.
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